feat: interfaces for async embeddings, implement async openai (#6563)

Since it seems like #6111 will be blocked for a bit, I've forked
@tyree731's fork and implemented the requested changes.

This change adds support to the base Embeddings class for two methods,
aembed_query and aembed_documents, those two methods supporting async
equivalents of embed_query and
embed_documents respectively. This ever so slightly rounds out async
support within langchain, with an initial implementation of this
functionality being implemented for openai.

Implements https://github.com/hwchase17/langchain/issues/6109

---------

Co-authored-by: Stephen Tyree <tyree731@gmail.com>

tests/integration_tests/embeddings/test_openai.py

@@ -1,6 +1,7 @@
 """Test openai embeddings."""
 import numpy as np
 import openai
+import pytest
 
 from langchain.embeddings.openai import OpenAIEmbeddings
 
@@ -26,6 +27,19 @@ def test_openai_embedding_documents_multiple() -> None:
     assert len(output[2]) == 1536
 
 
+@pytest.mark.asyncio
+async def test_openai_embedding_documents_async_multiple() -> None:
+    """Test openai embeddings."""
+    documents = ["foo bar", "bar foo", "foo"]
+    embedding = OpenAIEmbeddings(chunk_size=2)
+    embedding.embedding_ctx_length = 8191
+    output = await embedding.aembed_documents(documents)
+    assert len(output) == 3
+    assert len(output[0]) == 1536
+    assert len(output[1]) == 1536
+    assert len(output[2]) == 1536
+
+
 def test_openai_embedding_query() -> None:
     """Test openai embeddings."""
     document = "foo bar"
@@ -34,6 +48,15 @@ def test_openai_embedding_query() -> None:
     assert len(output) == 1536
 
 
+@pytest.mark.asyncio
+async def test_openai_embedding_async_query() -> None:
+    """Test openai embeddings."""
+    document = "foo bar"
+    embedding = OpenAIEmbeddings()
+    output = await embedding.aembed_query(document)
+    assert len(output) == 1536
+
+
 def test_openai_embedding_with_empty_string() -> None:
     """Test openai embeddings with empty string."""
     document = ["", "abc"]